<?php

/* SVN FILE: $Id: SassVariable.php 49 2010-04-04 10:51:24Z chris.l.yates $ */
/**
 * SassVariable class file.
 * @author      Chris Yates <chris.l.yates@gmail.com>
 * @copyright   Copyright (c) 2010 PBM Web Development
 * @license      http://phamlp.googlecode.com/files/license.txt
 * @package      PHamlP
 * @subpackage  Sass.script.literals
 */

/**
 * SassVariable class.
 * @package      PHamlP
 * @subpackage  Sass.script.literals
 */
class SassScriptVariable
{
    /**
     * Regex for matching and extracting Variables
     */

    const MATCH = '/^(?<!\\\\)(?(?!!important\b)[!\$]([\w-]+))/';

    /**
     * @var string name of variable
     */
    private $name;

    /**
     * SassVariable constructor
     * @param string value of the Variable type
     * @return SassVariable
     */
    public function __construct($value)
    {
        $this->name = substr($value, 1);
    }

    /**
     * Returns the SassScript object for this variable.
     * @param SassContext context of the variable
     * @return SassLiteral the SassScript object for this variable
     */
    public function evaluate($context)
    {
        return $context->getVariable($this->name);
    }

    /**
     * Returns a value indicating if a token of this type can be matched at
     * the start of the subject string.
     * @param string the subject string
     * @return mixed match at the start of the string or false if no match
     */
    public static function isa($subject)
    {
        // we need to do the check as preg_match returns a count of 1 if
        // subject == '!important'; the match being an empty match
        return (preg_match(self::MATCH, $subject, $matches) ? (empty($matches[0]) ? false : $matches[0]) : false);
    }

}